816721605 has 96 divisors (see below), whose sum is σ = 1702471680. Its totient is φ = 354119040.

The previous prime is 816721589. The next prime is 816721637. The reversal of 816721605 is 506127618.

816721605 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 816721605 - 2⁴ = 816721589 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 816721605.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 1006650 + ... + 1007460.

It is an arithmetic number, because the mean of its divisors is an integer number (17734080).

Almost surely, 2^816721605 is an apocalyptic number.

It is an amenable number.

816721605 is an abundant number, since it is smaller than the sum of its proper divisors (885750075).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

816721605 is a wasteful number, since it uses less digits than its factorization.

816721605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 991 (or 988 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The square root of 816721605 is about 28578.3415369052. The cubic root of 816721605 is about 934.7411200509.

The spelling of 816721605 in words is "eight hundred sixteen million, seven hundred twenty-one thousand, six hundred five".